The disclosures of U.S. Pat. Nos. 4,955,483 and 4,971,686 are incorporated herein by reference. Those patents, which are assigned to the assignee of this application, disclose a mail handling machine with a main flowpath along which envelopes are serially transported. The envelopes are horizontally oriented for transport along a deck. The envelope flap is under the body of the envelope, i.e. between the body of the envelope and the deck. The envelope may either be sealed or unsealed.
If the envelope is unsealed, the machine opens the envelope flap at a flap opening station. In its open position, the flap extends downwardly, forming an angle of about 25.degree. with the envelope body. The flap passes through a slot that extends beside the transport deck downstream from the opening station. While passing through the slot, the flap is moistened and subsequently the flap is sealed.
As disclosed in the above-cited patents, the flap opening station includes a pivotally mounted knife blade and a fixed guide edge that is spaced a short distance downstream from the blade. In the intended mode of operation of the opening station, the blade forces the flap open and, together with the guide edge, directs the flap into the slot. However, it has been found in some cases that the opened flap passes between the blade and the guide edge, resuming a horizontal, closed position rather than the desired downwardly extending open position. It is therefore desirable to modify the opening station so as to achieve more consistent opening of closed, unsealed envelopes.